Views:98 Author:Ronsco Publish Time: 2021-05-25 Origin:Ronsco
The production characteristics of large forgings are: large shape and weight, high quality requirements, multiple product varieties, single piece and small batch production, and long product production cycle.
Generally, the forgings produced by the free forging hydraulic press of 10 MN and above are called large forgings, which are equivalent to shaft forgings with a unit weight of more than 5t and cake forgings with a unit weight of more than 2t.
The main varieties of large forgings include:
Rolling mill forgings, such as cold and hot rolls, etc.
Forgings of forging equipment, such as columns and cylinders of hydraulic presses.
Thermal power forgings, such as generator rotors, guard rings, steam turbine rotors, impellers, etc.
Hydropower forgings, such as the main shaft and mirror plate of a hydroelectric generator.
Nuclear power plant forgings, such as pressure shells, evaporator cylinders, tube sheets, etc.
Petrochemical pressure vessel forgings, such as cylinders, flanges and heads of high-pressure vessels.
Marine forgings, such as stern shafts, intermediate shafts and crankshafts of marine engines.
Cement equipment forgings, such as gear rings, etc.
Forgings of mine hoisting equipment, such as main shafts.
Inner and outer rings for extra-large bearings.
Modules for forging hammers and presses.
Military forgings, such as artillery barrels, pressure shells of nuclear submarine nuclear vessels, turbine discs of jet engines, etc.
Various axles of railway vehicles.
The main shaft of large AC and DC motors.
There are many kinds of forgings in the above range, with different specifications, each with its own characteristics. This brings greater difficulties to production technology preparation and production plan management.
Heavy machinery, especially large steel rolling and forging equipment, are produced in one piece, and large forging blanks are also produced in one piece at one time. One set of crafts, there are many special crafts and equipment, and there are fewer opportunities for reuse. Some large forgings that are "tools", such as cold and hot rolls used in metallurgical plants, are also produced in small batches. When producing large forgings, it must be successful once. This requires full technical preparations before production, including various process verifications and experimental studies, which are time-consuming and labor-intensive and high production costs.
For large forgings produced in single or small batches, production preparations are complicated and the production cycle is long.
1) The preparation of metallurgical attachments is complicated. For example, a 600MW generator rotor, ranging from smelting and pouring steel ingot molds, lifting slings, transportation aids, to large auxiliary tools for forging, heat treatment and rough processing, etc., the total weight of the auxiliary tools, production hours, production cycle and production The cost is much more than the production of basic parts.
2) The research on various topics and the formulation and implementation of process plans before the production of large forgings have a long period.
3) Due to the large weight of large forgings, the production cycle is long. Including charge preparation, smelting, ingot casting, forging, first heat treatment, second heat treatment, rough machining and various inspections.
Large forgings generally require high quality and demanding technical conditions. This is especially true for power station forgings. It has chemical composition (including gas content), mechanical properties (tensile and impact properties), non-destructive inspection (ultrasonic inspection and magnetic particle inspection), metallographic inspection (grain size, inclusions), size and surface roughness of steel, All have extremely strict standards and requirements.
The production of large forgings, from smelting, ingot casting, forging, post-forging heat treatment to performance heat treatment, has to go through many processes. Each process affects the quality of forgings. A slight deviation may cause defects, so production is difficult.